We propose to continue and complete a randomized double-blind clinical trial of the efficacy of beta-carotene in preventing non-melanoma skin cancer in persons at high risk for this condition. This is a collaborative investigation conducted at four clinical centers with a separate data coordinating center. A total of 1805 patients have been entered and randomized to either beta-carotene, 50 mg per day, or placebo. They were identified from records of dermatology services and pathology laboratories at the four participating institutions and each had a proven diagnosis of either basal or squamous cell carcinoma of the skin since January 1, 1980. Each undergoes a total skin examination yearly with biopsy and independent dermatopathological examination of all suspicious lesion. Blood has been drawn for beta-carotene and retinol analyses at study entry and yearly thereafter. Every four months study participants complete a questionnaire providing information on compliance with the drug regimen, possible side effects experienced, and dermatological and non-dermatological conditions occurring in the interval. This application is for the final three years of a projected ten year study. It will allow us to complete five years of follow-up for all subjects and to analyze and report study results.